The present invention generally relates to twist-tie ribbons and in particular relates to a machine for applying a twist-tie ribbon to an article.
A twist-tie ribbon fastener is typically secured about an article by encircling the article with the tie ribbon and then twisting the ends of the twist-tie about each other to tighten the twist-tie into secure engagement about the article. Various devices have been proposed for applying a twist-tie to an article to securely fasten the twist-tie about the article.
One type of known device employs a ring for positioning a twist-tie ribbon about an article to encircle the article and has a gripping and twisting means that holds the ends of the twist-tie in close proximity to each other and then twists the ends of the tie ribbon about each other. A positioning means maneuvers the twist-tie ribbon along the ring and into engagement with the gripping and twisting means. The twisting and gripping means of these devices include a twister head that is rotatable about its axis to twist the ends of the ties about each other. A pair of push rods extend within the gripping/twisting means head and selectively traps the ends of the twist-tie against a portion of the head. In these devices, sliding extension and retraction of the push rods is controlled either by a rack and pinion system in combination with a rotating cam or by an air cylinder system which causes a complex of linkages to cause the push rods to be extended or retracted. Examples of these prior devices are found in Dilley U.S. Pat. No. 4,177,842, Mead et. al. U.S. Pat. No. 3,898,924, Hilton U.S. Pat. No. 3,318,230.
In a modification of these known devices, a twisting/gripping means includes a hook system which pulls the twist-tie against the head to grip the ends of the twist-tie (instead of trapping the tie ribbon by pushing an end of the tie ribbon against a portion of the head). For example, see Dilley U.S. Pat. Nos. 4,559,977 and 4,655,264.
In these prior devices, the timing and sequence of positioning a twist-tie about an article, gripping the ends of the twist-tie, and twisting the ends of the tie about each other are typically controlled by the relative dimensions, curved shapes, and positioning of a rotating cam or by the shapes and dimensions of a complex linkage system. For example, these prior devices have several linkages, which move in varying directions, to accomplish simple linear movement of a push rod for gripping a twist-tie end. In addition, the varying shape of the outer surface of the rotating cam causes the speed of movement of the tie ribbon to vary, which causes some slippage of the tie ribbon relative to the driving rollers of the device. These mechanical linkages and cam systems make it difficult to adjust the timing and sequence of functions of the devices since any significant changes in timing or sequence would require replacing a cam or linkage system. This inability to readily adjust operation of these devices limits their uses to a narrow set of applications.